For this project, we seek to do a secondary data analysis of the National Longitudinal Study of Adolescent Health (Add Health) data in order to understand the reason why individual differences (i.e., cognitive ability and personality) are related to health outcomes (a field called cognitive epidemiology). Many studies in cognitive epidemiology have shown a relationship between individual differences, measured in childhood/adolescence, and middle-to-late adulthood health outcomes. However, because the time points are so distal, they are unable to explain why such relationships exist. One method that can aid in understanding the individual differences health outcomes causal pathways is to use more proximal time points. The Add Health project is a nationally representative study, designed to explore the causes of health-related behaviors in adolescents and their outcomes in young adulthood. The respondents used in the project provide a nationally representative sample of the1995 population of American adolescents. During Wave I of the Add Health project (collected between 1994 and 1995), data was gathered on participants'cognitive ability (via a picture vocabulary test) and personality (the trait used for this project is Conscientiousness). The average participant age during Wave I was 15.61. Wave III of the project (collected between 2001 and 2002) contains information on participants'health outcomes (the ones used in this study are: (a) death, (b) body mass extremes [obesity and underweight], (c) diagnosed depression, (d) diagnosed diabetes, (e) physician reported high blood pressure/hypertension, and (f) physician reported high cholesterol). The average participant age during Wave III was 21.99. To analyze the data, we will utilize a path modeling approach, comparing a priori developed models that specify different pathways between individual differences and health outcomes. We will use the models to examine the following: (a) the relationship between cognitive ability and personality, and their mutual influence on health outcomes;(b) the relationship between individual differences and health outcomes after adding other covariates (e.g., SES, education level, health insurance) to the model;and (c) the relationship between individual differences and health outcomes as a function of health outcome severity. The importance of this project is twofold. First, knowing the influence of individual differences on health outcomes for young adults can help with public health policy and interventions by indicating areas where individual differences need to be used in planning/intervention. Second, this project's results can help elucidate the behaviors that adolescents and young adults engage in to cause the relationships between individual differences and health outcomes, which, in turn, could also be used also be used in planning public health interventions. PUBLIC HEALTH RELEVANCE: This research will test different hypotheses why individual differences (i.e., cognitive ability and personality) and health outcomes are related. By examining the relationship between individual differences in adolescence and health outcomes in early adulthood, and combing the results with the burgeoning literature in cognitive epidemiology showing the relationship between individual differences in childhood/adolescence and health outcomes in late adulthood, these studies can aid in the development of causal models concerning individual differences and health outcomes. These causal models, in turn, can then be used to develop appropriate health interventions across the lifespan.